Force nested arrays

[markmelville]

I've had no luck figuring out this nuance. I'm trying to convert data to a timeseries format required by another system. It wants the data as an array of arrays like this: http://try.jsonata.org/BkKNErBxL
Input:

[
  {"epochSeconds":1578381600,"value": 3},
  {"epochSeconds":1578381700,"value": 5}
]

Expression: $.[value,epochSeconds]
Result:

[
  [3,1578381600],
  [5,1578381700]
]

This is correct, but when there is only one item in the input array the result gets flattened.
Input:

[
  {"epochSeconds":1578381600,"value": 3}
]

Desired Output:

[
  [3,1578381600]
]

What I'm getting:

[
  3,
  1578381600
]

Is there some way to force an outer enclosing array when there is only one data point? TIA

[andrew-coleman]

It's a good question. I would have expected the following expression to work:

$.[value,epochSeconds][]

I.e. The result is a singleton sequence containing an array value. The [] should turn the sequence into a JSON array.

But this is clearly not working. I'll mark this as a bug and endeavour to fix it. Thanks!